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Why a test that tells when TB is cured is needed to help tackle resistance
Author: Prof Gerhard Walzl
Published: 14/03/2017

​​This article was originally published on The Conversation. Read the original article.

Every day more than 6 million people across the world who have TB are subject to a standard treatment regime. This lasts at least six months. The medication must be taken diligently every day to prevent drug-resistance from developing. Shortening the treatment period has become a top priority within TB research. US and South African scientists are embarking on a clinical trial to try and find a solution. The Conversation Africa's Health and Medicine Editor Candice Bailey asked Gerhard Walzl to explain the importance of the trial.

What are the current challenges around TB treatment?

In 2015 there were an estimated 10.4 million new TB cases worldwide. Six countries accounted for 60% of them: India, Indonesia, China, Nigeria, Pakistan and South Africa.

TB treatment is long and complicated to administer. It also has severe side effects.

To prevent the disease from reoccurring after treatment patients must take a combination of different antibiotics for at least six months. But the side effects linked to this antibiotic combination often include mild but annoying symptoms. In rarer cases the side effects can be severe and can include jaundice due to drug-induced liver disease.

The milder side effects include a general feeling of unwellness with nausea or loss of appetite, dizziness, skin rashes, sensations like pins and needles in the limbs or around the mouth, or flu-like symptoms. This often leads people, particularly in the later stages of the treatment period, to stop taking the medication. The problem is that this can result in multi-drug-resistant TB (MDR-TB) developing.

In 2015 there were an estimated 480 000 new cases of multidrug-resistant TB (MDR-TB).

To treat drug-resistant TB can take up to two years – and is even more complex, expensive and toxic. There's also a staggering cost attached to this treatment, which poses a significant challenge to governments, health systems and other payers.

In addition many patients are unable to even access treatment. Among those who do receive treatment for MDR TB, only 50% survive.

Can this lengthy process be shortened?

Shortening of standard treatment has become a top priority within TB research.

According to the studies, 95% of TB patients are cured with six-month courses while only 80% to 85% of patients are cured with shorter courses.

What this means is that most patients are cured after four months. The challenge is that scientists are unable to tell beforehand which patients belong to which group.

If it were possible to identify the patients who only require four-month therapy we would be able to reduce treatment duration in the vast majority of patients.

How have scientists tried to reduce treatment time and why has it not worked? How can this be changed?

Previous studies into the viability of shortening treatments to four months have been unsuccessful. New drugs were used in four-month treatment regimens in the hope that they could replace the longer treatments. But the rates at which the infection recurred were unacceptably high. Our hypothesis is that not all patients are suitable for shortened treatment regimens, regardless of the effectiveness of the new drugs and that a more individualised approach might be required.

Over the next five years the Predict-TB consortium, which includes five TB research groups in Cape Town, five in China and three institutions in Europe will address the problem.

The project will develop a smart set of treatment stopping criteria that are based on special lung scans (PET/CT imaging) as well as a point-of-care device which can measure the immunological markers that contribute to the decision on whether or not to stop treatment. These are proteins in the blood, whose levels are affected by inflammation and their levels will be measured by strip tests, similar to finger stick tests used to measure blood sugar levels.

These parameters will answer two key questions: is it possible to identify patients who are cured during a shorter treatment duration, and what combination of parameters can best identify these patients?

If treatment could be shortened, what would that mean for the treatment of TB?

This new method – if successful – could be a true game changer. It will advance treatment standards from the current practice of "one size fits all" to precision-guided individualised therapy. This will allow for shortened treatment in a significant proportion of drug sensitive TB patients.

The benefits would extend beyond patients, who would receive treatment for shorter periods and with better completion rates. Reducing the TB burden will also have an effect on the economic situation in many developing countries and less drug resistance will benefit public health on a global scale.

 

Gerhard Walzl is the head of the Immunology Research Group at the Division of Molecular Biology & Human Genetics, Department of Biomedical Sciences, Faculty of Medicine & Health Sciences, Stellenbosch University.